In May, the Padres and White Sox agreed to a deal for Peavy, but he turned it down. This time, Peavy agreed to waive his no-trade clause and join the AL Central contenders.

"The ultimate decision was when the team you're playing for actively keeps telling you they need to move you, and one team comes after you like Chicago did, you're excited to play for a team where you know you're wanted," Peavy said during a news conference in San Diego.

"In May, we didn't think it was the right time, but now things are a little bit different on a lot of fronts. ... I think the only reason this deal was able to get done is because they did pursue it actively in May. In May, we had just won five or six games in a row and had creeped above .500, and Chicago wasn't really in the shape that they're in now."

The White Sox began play Friday in third place in the AL Central, 2½ games behind first-place Detroit.

White Sox general manager Ken Williams was not discouraged by the initial rejection from Peavy.

"He never said no, he just said 'not yet,' " Williams said.

"So those words 'not yet' for me meant just that. ... If you are patient in your pursuit, then sometimes you can ultimately get what you want," he said. "When we called back this time, he was better prepared -- he and his family were better prepared for what lies ahead. We were all able to make it work."

The 28-year-old Peavy is 6-6 with a 3.97 ERA in 13 starts with the Padres this season but has been on the disabled list since June 13 with a strained tendon in his right ankle. Williams said the White Sox don't expect Peavy to pitch until the end of August and he could go on a rehab assignment in the middle of the month.

"We're going to still be conservative with our approach. In our division this thing is going to go down to winning games in September," Williams said. "We want to be as strong as we possibly can in September. That's what we're focused on."

Peavy agreed, saying said he should be ready by the end of August.

Over eight major league seasons with the Padres, Peavy is 92-68 with a 3.29 ERA and 1,348 strikeouts in 212 starts. He was a unanimous selection for the Cy Young Award in 2007 when he went 19-6 with a 2.54 ERA and 240 strikeouts in 34 starts.

Until then the White Sox will have to mix and match to find a fifth starter with Bartolo Colon injured and Richard off to San Diego.

Williams said he called Padres general manager Kevin Towers on Friday morning and got talks rekindled. Peavy's agent, Barry Axelrod, went to Peavy's house and Williams said the deal was completed mere seconds before the 3 p.m. CDT deadline.

Williams said he'd been interested in Peavy since the trade deadline a year ago and then was close to landing him in May. This time he worked on the trade with few people even knowing about it.

"I was shocked," White Sox manager Ozzie Guillen said. "We got better and now we got one guy we wanted for a long time."

Williams said he had a good talk with Peavy when the White Sox first tried to acquire him. He was convinced that Peavy's real reason for blocking the trade was that he wasn't ready.

"At the time the Padres were in just as good a position as we were [and] to have it sprung on him without all the information," Williams said. "I got it. I understood. It was a little disheartening to hear some of the insinuations about him not wanting to pitch in the American League or pitch in our ballpark. I got none of that when I spoke to him. It was simply about him being surprised."

Now Peavy, whose future has been the subject of much speculation since the offseason, is ready to move on. He is making $11 million this year.

He will have a salary of $15 million in 2010, $16 million in 2011 and $17 million in 2012. His initial contract included a $22 million club option for 2013 with a $4 million buyout.

"I certainly knew this day was going to come, whether it be now like it's happening or in the offseason. Now it's here, and I'll go to Chicago and I won't look back," Peavy said.

Richard, who pitched well in his past two starts, was the scheduled starter Friday night against the Yankees before the trade was announced.

The 25-year-old lefty was 4-3 with a 4.65 ERA in 26 games, including 14 starts, with the White Sox this season.

"Pretty surprised," Richard said, sitting in the dugout after the trade was announced.

"Because I really just thought he didn't want to come over here. He turned it down and it was put to rest. Then, out of nowhere, it happens again. But I'm excited to go over there. We'll see how it goes."

Poreda, 22, went 1-0 with a 2.45 ERA and 12 strikeouts in 10 relief appearances with the White Sox before being optioned back to the minors on July 21. The 6-foot-5 lefty was a first-round pick by Chicago in 2007.

Russell was 4-0 with a 5.19 ERA in 22 relief appearances for the White Sox last season and has spent this year at Triple-A Charlotte. Carter is 6-2 with a 3.13 ERA at Class-A Kannapolis.